Bug 1932: Fixed bugs in InetMatch.

  * equals(Object) does not work.
  * An empty string specified via JAXB as a string representation of
    IP address should be rejected.

Other changes:

  * Add unit tests for flow condition APIs.
  * Reduce sonar warnings in FlowMatch and FlowMatchBuilder.

Change-Id: I795d855279751a893fc4a93e547aafd528cbb021
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>